Sludge exclusion diaphragm switch



Dec. 19, 1967 w. F. HOWARD 3,359,386

SLUDGE EXCLUSION DIAPHRAGM SWITCH Filed Oct. 11, 1965 FIG.I

. INVENTOR. WILLlAM F. HOWARD BY J A TORNEYS United States Patent ABSTRACT 0F THE DISCLOSURE A sludge exclusion device is shown, specifically as embodied in a diaphragm-operated switch unit, in which a housing structure of the device is sub-divided into two spaces by means of a flexible diaphragm fixedly clamped marginally between coaxial housing parts. The upper-most of these parts receives an electric switch, which is adapted to be operated by the diaphragm upon predetermined pressurization of the latter on the side thereof opposite the switch. The device is completed by a protective diaphragm connected across the open bottom of the lower housing part, thereby defining, in conjunction with the first-named diaphragm, a pressure space which is adapted to be variably pressurized upon immersion of the device in a liquid-filled sump or like accumulator. The two diaphragms are wholly exposed to one another throughout their respective areas on opposite sides of the pressure space.

The protective diaphragm is of considerably greater flexibility than the diaphragm, being variably deformed by hydrostatic pressure under immersion in a body of liquid. Regardless of the temperature of that liquid the device uniformly transmits hydrostatic head force to the upper diaphragm through the compressed fluid between the latter and the protective member; and the latter, of course, protects the diaphragm and the interior of the housing of the device. It is automatically self-cleaning by reason of its freely flexing, quite floppy nature.

The present invention relates to a hydrostatic pressure responsive, diaphragm type switch having improved provision, in the form of an external protective diaphragm, for the exclusion from a basic or master switch-operating diaphragm of the unit of sludge, grease, soap and other foreign matter which might otherwise accumulate and incrust thereon. Such deposits or incrustations are highly undesirable, since they render the actual switch-operating diaphragm objectionably insensitive in response to hydrostatic pressure variations in a tank or other accumulator in which the switch unit is immersed, for example in the control of a pump or valve associated with the tank.

The improvement represented by the auxiliary diaphragm of the invention prevents this and at the same time protects itself, by in the first place sealing off and blocking access of the liquid-entrained foreign matter to the actual switch-operating diaphragm and, in the second place, by automatically preventing its own accumulation of any significant amount of such matter, i.e., it is selfcleaning.

For this purpose, and in accordance with one object, the invention provides an external sealing diaphragm of quasi or generally semi-spherical, outwardly convex shape which is in liquid-tight engagement with a skirt-like part of the housing structure of the switch unit, thus sealing the interior of this housing portion from the sludge or otherwise contaminated or entrained liquid. The master diaphragm exposed on one end of the housing skirt is thus permanently protected.

In further accordance with the objectives of the invention, the auxiliary self-cleaning exclusion diaphragm is fabricated of a suitable deterioration-resistant material,

3,359,386 Patented Dec. 19, 1967 ice such as natural or synthetic rubber, a synthetic resinous or like composition, or possibly a suitably impregnated fabric, in a quite thin-walled cross section, so as to be very flexible, in fact physically unstable and floppy. This renders the diaphragm sensitivity responsive to external hydrostatic pressure, regardless of variation in volume of the air in the switch housing skirt between it and the operating diaphragm under temperature changes. Pressure is faithfully transferred to the latter member through the variably compressed air, the two diaphragms being directly and wholly exposed to one another, and to the pressure space therebetween, across their entire respective areas. Hence response of the device under different hydrostatic pressures is quick and accurate, and notwithstanding changing temperatures of the liquid medium in which the devise is immersed.

It is also evident that the exclusion diaphragm can be used to sense and respond on the basis of such temperature changes, under variable or constant hydrostatic pressure.

The foregoing as well as other objects will become more apparent as this description proceeds, especially when considered in connection with the accompanying drawing illustrating the invention, wherein:

FIG. 1 is a fragmentary side elevational view of the improved switch unit, the normal, fully relaxed outline of its protection or exclusion diaphragm at atmospheric pressure being typically shown in solid line, and in dotted line as subjected to a given hydrostatic pressure of immersion liquid under normal room temperature;

FIG. 2 is a similar side elevational view showing in solid line and approximate outline taken by the protective diaphragm at some intended maximum operating temperature, the corresponding diaphragm position for a minimum operating temperature being shown in dot-dash line; and

FIG. 3 is a view in vertical diametral section through the switch unit, showing internal diaphragm and electric switch means thereof.

The switch unit, generally designated by the reference numeral 10, comprises a hollow housing 12 made up of a cast upper dome portion 14 of circular cross section and a lower cylindrical skirt portion 16; and these housing parts are (FIG. 3) separated in sealed relation to one another by a flat master or switch-operating diaphragm 18 and a sealing washer or gasket 20. Diaphragm 18 may be of synthetic or natural rubber in a selected thickness for intended flexure under the contemplated operating conditions, or it may be an impregnated or corrugated metal type. Gasket 20 is preferably of rubber, and the diaphragm and gasket are tightly clamped between bolted flanges 22 and 24 of the respective housing parts.

Diaphragm 1 8 is shown in FIG. 3 as provided with a rigid central pressure plate 26 adapted to make and break engagement with the actuator button of a conventional microswitch 28 fixedly within the upper housing part, the electrical lead cable 30 of this switch being brought through an adjustable tubular connector 32 threaded into a top boss 34 of the part 14. Switch 28 is fixed to connector 32, which upwardly communicates the space in housing dome 14- with atmosphere.

The reference numeral 36 generally designates the protective or sludge excluding diaphragm of the switch unit 10. Like the switch-operating diaphragm 18, diaphragm 36 is directly and wholly exposed across its entire area to the space whose top and bottom they define. It is molded in a quasior approximately semispherical, outwardly convex and protuberant cross section, with a radially inwardly extending, annular upper beaded flange or rim 38, which has liquid-tight, overlapped and snap-on sealing engagement with an integral outer bottom flange 40 of the housing skirt 12, as best shown in FIG. 3. Other fluid pressure-tight types of connection may of course be used. As indicated above, the protuberant membnane or diaphragm may be fabricated of natural or synthetic rubber, a suitable synthetic plastic, such as Teflon, an impregnated fabric, or the like.

As compared with the basic operating diaphragm 18, diaphragm 36 is quite thin and flexible, thus being very sensitively reactive in response to variations in hydrostatic pressure of the liquid in which switch unit is immersed. It effectively seals of]? the space directly be neath diaphragm 18 against entry of liquid-entrained matter, such as grease, soap or other sludge content. Likewise, in flexing in a range of contours indicated in solid and dotted line in FIG. 1 and in solid and dot-dash line in FIG. 2, the exclusion diaphragm 36, due to its rather structurally instable (even floppy) nature, automatically prevents its own incrustation, immediately dislodging any deposit of entrained matter which might tend to commence. 7

FIGS. 1 and 2 depict the typical action of diaphragm 36 when subjected to a given hydrostatic pressure in water or other immersion liquid under different temperature conditions. Thus, assuming that switch unit 10 is intended to respond in the closing and opening of the electrical switch component 28 over a temperature range between a lower operating limit of, say 35 F. and an upper limit of, say, 140 F. and that the center area of diaphragm 36 will have a normal, relaxed solid line contour (FIG. 1), at room temperature, then the position of the diaphragm, as centrally displaced upwardly under the hydrostatic pressure at the room temperature is as shown in dotted line in FIG. 1.

Again, reference being had to FIG. 2, the central diaphragm displacement at the upper instanced operating temperature of 140 F. will, due to expansion of air thereabove, be as shown in solid line; while a greater upward deflection shown in dot-dash line occurs at the lower limit temperature. Accordingly, the exclusion diaphragm 36 is accurately responsive in transmitting appropriate force through the variably compressed air in housing skirt 16 to operating diaphragm 18 regardless of thermal change in the immersion liquid. As indicated above, it protects diaphragm 13 against becoming deteriorated or inadequately insensitive in action under exposure to sludge or other possible source of attack or incrustation, and protects itself by a self-cleaning flexure action.

When utilized as described above, in a switch whose space between diaphragms 18 and 36 is air or gas-filled, the exclusion diaphragm is sensitively responsive to changes in that internal pressure under varying temperature, as the gas expands and contracts; hence the unit is Well suited for a temperature responsive function, either under varying hydrostatic external pressure or constant hydrostatic pressure.

While the invention primarily concerns improvements in a switch unit, it is readily seen that the protective diaphragm as applied to a housing structure for an operating or control diaphragm, or equivalent fluid pressure responsive member, is applicable to various other types of related liquid immersed, pressure responsive types of unit. Obviously the improvements of the invention are exceedingly simple in nature, permitting low cost procurement and assembly, either in a unit of original manufacture, or in the conversion of a generally similar unit to the purposes of the invention.

What I claim as my invention is:

1. A fluid pressure operated unit, comprising a housing structure having a flexible, fluid pressure responsive diaphragm secured thereto and internally sealing a housing space on one side of said diaphragm, a protective diaphragm having a liquid tight connection across said structure on a side of said housing space remote from said first named diaphragm, and a volume of air or other compressible gas filling the space between said diaphragms, said protective diaphragm being flexible under external hydrostatic or similar pressure thereon to transmit a force arising from said pressure through said gas to said first named diaphragm, said protective diaphragm being of substantially greater flexibility than the first named diaphragm, to the extent of being floppy, hence self-cleaning.

2. A fluid pressure operated unit, comprising a housing structure having a flexible, fluid pressure responsive diaphragm secured thereto and internally sealing a housing space on one side of said diaphragm, a protective diaphragm having a liquid tight connection across said structure on a side of said housing space remote from said first named diaphragm, said diaphragms being directly and wholly exposed to said space across the entire respective areas thereof, and a volume of air or other compressible gas filling the space between said diaphragms, said protective diaphragm being flexible under external hydrostatic or similar pressure thereon to transmit a force arising from said pressure through said gas to said first named diaphragm, said protective diaphragm being of outwardly convex outline and substantially greater flexibility than the first named diaphragm, to the extent of being floppy, hence self-cleaning.

3. A fluid pressure operated switch unit, comprising a housing having a flexible, fluid pressure responsive diaphragm secured thereto and separating a switch space on one side thereof from another housing space on the other side thereof, an electrical switch mounted on said housing within said switch space so as to be operated by said diaphragm upon movement of the latter responsive to pressure in said housing space, a protective diaphragm having a fluid tight connection across said other housing space on a side of the latter opposite said first named diaphragm, and a volume of air or other compressible gas in said other housing space, said protective diaphragm being secured to said housing and being flexible under external hydrostatic or similar pressure thereon to transmit a force arising from said pressure through said gas to said first named diaphragm, said protective diaphragm being of substantially greater flexibility than the first named diaphragm, to the extent of being floppy, hence self-cleaning.

4-. A fluid pressure operated switch unit, comprising a housing having a flexible, fluid pressure responsive diaphragm secured thereto and separating a switch space on one side thereof from another housing space on the other side thereof, an electrical switch mounted in said housing within said switch space so as to be operated by said diaphragm upon movement of the latter responsive to pressure in said housing space, a protective diaphragm having a fluid tight connection across said other housing space on a side of the latter opposite said first named diaphragm, and a volume of air or other compressible gas in said other housing space, said protective diaphragm being secured to said housing and being flexible under external hydrostatic or simlar pressure thereon to transmit a force arising from said pressure through said gas to said first named diaphragm, said protective diaphragm being of an outwardly convex outline and substantially greater flexibility than the first named diaphragm, to the extent of being floppy, hence self-cleaning.

References Cited UNITED STATES PATENTS 2,435,716 2/1948 Kearney 20083.2 2,653,552 9/1953 Geeraet 200-83.2 3,176,095 3/1965 Conery ZOO-81 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner. 

1. A FLUID PRESSURE OPERATED UNIT, COMPRISING A HOUSING STRUCTURE HAVING A FLEXIBLE, FLUID PRESSURE RESPONSIVE DIAPHRAGM SECURED THERETO AND INTERNALLY SEALING A HOUSING SPACE ON ONE SIDE OF SAID DIAPHRAGM, A PROTECTIVE DIAPHRAGM HAVING A LIQUID TIGHT CONNECTION ACROSS SAID STRUCTURE ON A SIDE OF SAID HOUSING SPACE REMOTE FROM SAID FIRST NAMED DIAPHRAGM, AND A VOLUME OF AIR OR OTHER COMPRESSIBLE GAS FILLING THE SPACE BETWEEN SAID DIAPHRAGMS, SAID PROTECTIVE DIAPHRAGM BEING FLEXIBLE UNDER 